1. Field of the Invention
The present invention relates to a toner and a two-component developer.
2. Description of the Related Art
As a method for manufacturing a toner, a kneading and pulverization method is conventionally used. However, the pulverized toner particles are amorphous-shaped whose surfaces have a plurality of concavity and convexity. Since the fracture plane after pulverization directly becomes a toner particle surface, the surface composition of the toner particle easily becomes so nonuniform that it is difficult to control the surface condition to be uniform. When the toner particle surface is amorphous-shaped because of the plurality of concavity and convexity, problems are posed such that the flowability of the toner is degraded, fogging and toner spattering due to the nonuniformity of the toner composition is caused, and so on.
In view of such problems related to the amorphous-shape of the toner particle surface, instead of a kneading and pulverization method, a variety of methods for manufacturing a toner are proposed such as a wet method comprising mixing dispersion liquid of toner materials and aggregating the materials. However, in case of a wet method, since a dispersion stabilizer and an aggregating agent are heavily used, a part of their components remains on a toner particle surface or inside a toner particle, resulting in disadvantages to cause decrease of humidity resistance and degradation of chargeability, in particular, to easily cause the chargeability to be highly unstable.
Among properties required of toner, chargeability is particularly important, which significantly effects behavior and quality in development and transferability (control of color toning process and transfer process, and so on).
On the other hand, according to recent trends of high-quality imaging, downsizing of particle size of a toner is progressed and content percentage of a finely-divided toner having small particle size tends to be increased. In a two-component developer comprising a toner having small particle size, crack and shape change of the toner having small particle size caused by a stress in a developing apparatus cause toner spent on a carrier along with degradation of chargeability of the developer, which trigger degradation of image quality.
Further, according to recent trends of colorization, low-temperature fixing of a color toner is progressed and a toner whose component is softened at low temperature tends to be used.
Accordingly, a capsule toner is proposed as the toner having excellent flowability, transferability and the like, uniform chargeability, advanced offset resistance, and various capabilities other than the above, in which a surface of a toner base particle is coated with a resin layer.
In Japanese Unexamined Patent Publication JP-A 2006-293273, a toner is proposed which has core shell structure such that storage elastic moduli of a core layer and a shell layer have a predetermined ratio.
However, the storage elastic modulus of the shell layer of the toner disclosed in JP-A 2006-293273 is so greater than that of the core layer that exudation of the release agent during fixing is not easy, with the result that high-temperature offset phenomenon may occur.